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Scientists are uncovering the mysteries of a non-addictive painkiller... that lives in your mouth

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Written by: Jill Teige

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With so many ways that people can get hurt, researchers are always on the lookout for non-addictive ways to treat severe or chronic pain. And in 2006, they found a compound that may work even better than morphine called opiorphin.

It was hiding right under our noses... in human spit. In 2003, scientists found a similar compound in rat saliva, which is released in response to stressful situations, like being in pain. So the team went searching for one in humans too, and they found opiorphin.

To be totally clear, it’s not like this chemical is constantly numbing your mouth and body. Opiorphin naturally gets broken down in your digestive tract, so it doesn’t seem to stick around and have pain-relieving effects. And even if you’re the kind of person who licks their paper cuts, we’re not sure if it does anything on your skin, or if there’s enough of it to make you feel better.

Scientists figured out how opiorphin works by isolating it and doing experiments mostly not in whole living organisms. And its painkiller abilities are a little roundabout. Specifically, it binds to enzymes in the body that break down another class of pain-killing compounds called enkephalins.

Enkephalins are peptides — shorter amino acid chains. And kind of like endorphins, they bind to opioid receptors in the central nervous system and keep certain signals from reaching the brain, so you don’t perceive pain. Basically, they help make you feel good!

Since pain is a sign that something’s wrong, you can’t have enkephalins around all the time. So your body also has a group of enzymes called proteases that tidy up. They break down proteins and peptides, and help make sure the right signals are being sent and received.

Opiorphin blocks a couple specific proteases that break down enkephalins, so these pain-relieving chemicals stick around longer. Researchers think that compounds like opiorphin might exist because they help in times of danger — they block out pain to let us run away from whatever’s causing it in the first place. But to figure out what opiorphin is capable of, scientists ran a few different tests.

In one, they injected a chemical irritant called formalin into rat paws. . Not only that, but opiorphin seemed to be almost as effective as a slightly higher dose of morphine. The other was a pin-pain test, where the rats had to walk over a pin-covered surface.

Like a human on a bed of nails, the pins were close enough that the rats couldn’t stab themselves, but were still uncomfortable. Here, too, the researchers found that opiorphin seemed to work almost as well as morphine to keep the pain at bay. As far as we can tell from testing rats, opiorphin is less addictive than opioid painkillers like morphine.

And scientists think we’re less likely to become tolerant, or need more drug over time to get the same effects. Unfortunately, it’s also pretty likely that opiorphin doesn’t just block proteases that break down enkephalins — which might mean unwanted side effects. So we still have a lot of questions about what this painkiller is doing in our spit, and how to turn it into medicine.

But it’s a pretty cool find, and may be useful someday. But for now, even with a painkiller in your saliva, you can’t lick your own face to alleviate razor burn. You could maybe lick your armpits if you shave them, but would you want to?

And if you’ve ever tried to test out shaving cream and a razor in the store, you know that does not go over well. Luckily! The aptly named Dollar Shave Club is offering SciShow viewers their “Daily Essentials”.

Starter Set to new members for just $5. They’ll send you their Executive Razor, plus a full set of cartridges, as well as trial versions of their most popular products: Shave Butter, Body Wash, and One Wipe Charlies’. Butt Wipes.

You know you want those butt wipes. After the first month, they’ll send you replacement cartridges for your razor every month for just a few bucks. Go to to get The Daily Essentials starter set for just $5 and know that when you do, you’re also supporting SciShow.

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